The present invention relates to an electric compressor that has a power semiconductor module.
A typical electric motor used in an electric compressor is controlled by a power semiconductor module such as an inverter. When the compressor is driven, a great magnitude of electric current is supplied to the electric motor through the power semiconductor module. The power semiconductor module performs frequent switching, which generates a great amount of heat. It is therefore necessary to cool the power semiconductor module so that the module function properly.
A power semiconductor module may be cooled either by the outside air or by refrigerant that cools the compressor. A module that is cooled by the outside air has radiator fins or a fan to send air to the module.
The electric compressor disclosed in Japanese Unexamined Patent Publication No. 4-80554 has a power semiconductor module that is cooled by refrigerant. The module is attached to the circumferential surface of the housing of a compressor and is located between the compressing mechanism and the electric motor of the compressor. Heat generated by the module is absorbed by the housing. In the apparatus disclosed in Japanese Unexamined Patent Publication No. 8-14709, a power semiconductor module is attached to an accumulator that is located in an external refrigerant circuit so that refrigerant in the accumulator cools the module.
Radiator fins and a fan, which are used for cooling a power semiconductor module, increase the size of the module. Thus, a compressor that has such a module that is cooled by the outside air occupies a relatively large space.
In the compressor of the publication No. 4-80554, the cooling efficiency of the power semiconductor module, which is attached to the housing circumference, is not considered when determining the location from which refrigerant is drawn into the compressor housing. Therefore, the module is not effectively cooled. The apparatus disclosed in the publication No. 8-14709 requires members to attach a power semiconductor module to an accumulator. Further, since the harness for electrically connecting the module with the compressor is relatively long, it is troublesome to install the harness.
Accordingly, it is an objective of the present invention to provide a compact and inexpensive electric compressor that effectively cools a power semiconductor unit.
To achieve the above objective, the present invention provides an electric compressor. The electric compressor comprises a compression mechanism and an electric motor. The compression mechanism draws, compresses and discharges refrigerant gas. The electric motor drives the compression mechanism. A housing accommodates the compression mechanism and the electric motor. A power semiconductor module is located in the housing. The power semiconductor module powers the electric motor. A heat sink cools the power semiconductor module. The heat sink is cooled by the refrigerant gas.
Other aspects and advantages of the invention will become apparent from the following description, taken in conjunction with the accompanying drawings, illustrating by way of example the principles of the invention.